A detachable detecting device generally referred to as a probe is installed in the center of the magnetic field of a test section of an NMR apparatus. The probe is a detecting device which measures the magnetic moment of the atomic nucleus of a sample, and it is fitted with a sample tube in which the sample is placed. Radio waves (RF) are generated in the powerful magnetic field, and the emission or absorption of radio wave energy by the sample is measured by a detector. Although the construction of the probe varies according to the type of NMR apparatus, it usually has a space for inserting the test sample tube, fixing members for fixing the probe in the magnetic fields generated by a pair of magnet, RF sending and receiving coils, lead wires to the corresponding RF circuits, shim coils, and an RF preamplifier. The shim coils are placed in the magnetic field away from the probe, and the RF preamplifier may be installed separately from the magnetic field.
NMR systems may be broadly distinguished as solution systems, solid systems, and imaging systems (MRI). Although the principle is the same, the difference lies in the sample installation method, measurement method, and the devices used (spectroscope power, recognition system, and detector (probe), etc.) depending on the differences in the test sample. MRI can be distinguished from other devices because of its familiarity and user type. However, both solution systems and solid systems are used on the research level, therefore, if a person is not trained in the system, he may confuse these systems as if they were identical, but there are large differences between them, for example, it is difficult to use a sample tube across systems.
When performing a solid nuclear magnetic resonance (solid NMR) measurement, high resolution techniques are usually used to obtain a larger amount of information from the sample. This technique differs from technique arranging a sample tube parallel to a static magnetic field as is usually performed in solution NMR, but consists of a method irradiating a radio wave sent from a coil to strike the sample tube, which is inclined at a magic angle of 54.7 degrees relative to the static magnetic field and rotates at high speed in the coil. The property of the material in the sample can be examined by measuring an absorption by a sample or an emission from the sample based on said absorption of the radio wave. This method is called the magic angle rotating process, and is generally used in solid high resolution measurements (e.g., Nonpatent document 1 and 2).     [Nonpatent document 1] Roue, Phys. Rev. Lett. 2, 285, (1959)     [Nonpatent document 2] Andrew, Nature, 183, 1802 (1959)
When using the above-mentioned magic angle rotating process, it is necessary to rotate the sample stably at a high speed of 1,000 revolutions per second or more. In this case, a ceramic or polymer sample tube having a length of about 5 mm to 5 cm, and thickness of several millimeters to about 1 cm, is filled with the sample. This is inserted into the coil arranged in a housing. A gas, such as high-pressure air or nitrogen etc., is sprayed at least at higher part and lower part of the sample tube from the sample tube housing, and the sample tube is floated in the air. The sample tube is rotated at high speed inside the coil by sending high-pressure air into turbine-shaped vanes known as spinners at the end or the center of the sample tube (e.g., Patent document 1 and 2).     [Patent document 1]: JP-A 55-163447     [Patent document 2]: JP-A 58-154645
In order to realize a stable rotation at high speed, flotation bearing air is delivered by two or more (sample tube higher part and lower part) paths, and there is a rotation driving air system separated from the flotation system. To cause it to rotate stably, a housing is provided. Irradiation and detection of radio wave is performed by a solenoid coil surrounding the cylindrical sample tube which is fixed to the housing, and when the probe has been set in the magnetic field, this solenoid is attached so that it is inclined at 54.7 degrees to the static magnetic field. The housing part has at least a flotation air port, a rotation air port, and a terminal for irradiating/detecting radio wave, which can be connected with the outside via the probe body.
In the prior art, when performing the magic angle rotating method for a small amount of sample, (1) the diameter of the sample tube is made small so as to decrease the size of the whole sample tube, or (2) the length of the sample in the sample tube is shortened. However, in the case of (1), it was necessary to re-design the mechanism of the housing of the sample itself in the sample tube, and the sample housing in the observation probe had to be changed over during tests, which was complicated. Further, to perform a stable measurement, the sample must be rotated stably at high speed. However, if the diameter of the sample tube becomes small, the whole sample tube which is struck by the flotation gas also become small. Therefore, there was a defect that the rotation was not stable. In the case of (2), the irradiation of radio wave to the sample was low, and there was a serious defect that the signal detection sensitivity was low. It was therefore desired to develop a sample tube which could stably rotate a small amount of sample, and with which irradiation and detection of radio wave could be efficiently performed.
On the other hand, in the case of a solution, the sample is introduced into a glass test tube (about 15 cm length), fitted to a holder, and then introduced into a solution probe. Next, to cancel out non-uniformities of the sample in the XY direction relative to the magnetic field, the sample is rotated if needed. A rotation of about 20 rotations per second is usually sufficient for this purpose. In general, as for the rotation driving air, the same path for the flotation bearing air is used. Thus, in the case of solution NMR, the magic angle high speed rotation method performed by solid NMR is not used, and there is no housing, either. It is also not required that air strikes the higher part and lower part of the sample tube. This is however indispensable when performing a solid magic angle high speed rotation method. Therefore, in a solution system, the top end of the standard sample tube is made thin, and a micro sample is concentrated (Patent document 3) for measurement. However, in the magic angle high speed rotation method in solid NMR, stable high speed rotation cannot be performed by simply using a sample tube having a thinner top end.     [Patent document 3]: JP-A 55-101342